Mark 4 Coach Compatibility

[Covkid]

On 06/06/2022 at 23:02, Wickham Green too said:

Does the air pressure actually have to be created on the locomotive ? ..... with a two pipe system Id've thought they could fit an engine driven compressor in the vastness of the support coach and just fit the application valve on the loco.

 

15 hours ago, jim.snowdon said:

No, and what you propose is pretty much the way it works on a multiple unit.

 

True Jim, but it is only feasible if the formation doesnt change en route a la multiple unit.  You would have issues at terminals where you would need to run round or shunt, and i am not convinced the ORR would be too keen. There are however places on a steam loco that an airpump can be located. I think one of the GWR Castles has a pump somewhere and 6024 has one between the frames. Clan Line and one of the Stanier pacifics has it on the back of the tender. Perhaps horizontal partly hidden by the running plate might be another option, but bearing in mind they use live steam, and steam condenses when it cools i would imagine the pump needs to be near the supply of hot live steam.

[Wickham Green too]

27 minutes ago, Covkid said:

.... the pump needs to be near the supply of hot live steam.

Which is why I said engine-driven compressor ...... after all there's an engine-driven generator for the ETH hidden somewhere already ( unless the 'assisting' diesel is 'assisting' with that task ).

[roythebus1]

There shouldn't be a problem having a twin-piped loco with no compressor at the head of a train with another loco elsewhere in the train providing the main air supply. As someone else said, this is how multiple units work. 4VEP for instance the compressor is in the motor coach in the middle of the train.

 

It won't work with a single pipe air system, but the drivers brake valve will still be able to apply the brake; it just won't be able to release it unless there is an air supply on the loco. 

 

I learnt all about Westinghouse air brakes when I joined the underground as a guard in 1970, and later on BR on the suvvern, and as a guard on the IWSR. so very familiar with how they used to work. :)

[jim.snowdon]

On 08/06/2022 at 08:23, Covkid said:

True Jim, but it is only feasible if the formation doesnt change en route a la multiple unit.  You would have issues at terminals where you would need to run round or shunt, and i am not convinced the ORR would be too keen.

The primary requirement is that, as a passenger train, the brake is applied automatically in the event of a division (as per the 1889 Regulation of Railways Act). The critical element in this, for the Automatic Air Brake, is the Brake Pipe. The principal purpose of the Train Pipe is as a means of providing pressurised air to the brake control valve. The source and the control valve can be on different vehicles. The compressor could be on a support carriage within the train, and the locomotive at one or other end of the train. Running round is not a problem, as long as the locomotive has an independent means of braking - as is normally the case. Splitting the train en route is not a problem either, so long as the vehicle carrying the compressor remains with the locomotive.

 

Thinking about it, that is exactly what happened with the 4REP/33+TC sets that were used for the Waterloo - Weymouth services. Leaving Waterloo, the driver's brake control valve was at the front of the train, whilst the compressor was 8+ cars away on the 4REP at the back of the train. On arriving at Bournemouth, that would be uncoupled and replaced by the 33 (with its compressor) at the front of the train. Before anyone comments, I am aware that these units also had electro-pneumatic brakes, for which the Train Pipe also functions as an air main for the individual carriages, but that is a system that is overlaid on the standard Westinghouse type air brake which remains fully functional in its own right (and provides compliance with the 1889 Act).

[Ken.W]

On 03/06/2022 at 22:24, Steven B said:

 

As far as the Mk4 is concerned, it wouldn't be impossible to relocate door control and parking brake equipment from the DVT into a modified TSOE to make a TSOBE. The Electric train supply needs would restrict their use on preserved lines unless they were fitted with a generator. Probably far too much work for the vast majority of railways. There may be scope for train tour sets such as with the refurbished Blue Pullman HST and Intercity Mk3a sets.

 

Steven B.

 

Well, not impossible, but it would mean expensive work messing about with complicated equipment which can be temperamental enough as it is.

But then, where does that get you?

Too much, as you say for preserved lines, plus you can't just go making significant alterations to safety critical systems as such changes would invalidate their "Grandfather Rights" derogation to operate on NR for railtour use,  meaning they would need recertification of Type Approval to operate on the national system, a long and extremely expensive process, and possibly to modern standards which would they now pass anyway. This was, we were told at the time, the reason why despite all the problems with them, GNER dropped plans to replace the air-con systems.

 

As to all the discussions about where the compressor for air brakes needs to be, erm, we are talking about Mk4s here, they've only be running for approx the last 30+ years with the compressor at the rear for 50% of the time.

Edited June 17, 2022 by Ken.W

[DY444]

On 10/06/2022 at 17:56, jim.snowdon said:

 

Thinking about it, that is exactly what happened with the 4REP/33+TC sets that were used for the Waterloo - Weymouth services. Leaving Waterloo, the driver's brake control valve was at the front of the train, whilst the compressor was 8+ cars away on the 4REP at the back of the train. On arriving at Bournemouth, that would be uncoupled and replaced by the 33 (with its compressor) at the front of the train. Before anyone comments, I am aware that these units also had electro-pneumatic brakes, for which the Train Pipe also functions as an air main for the individual carriages, but that is a system that is overlaid on the standard Westinghouse type air brake which remains fully functional in its own right (and provides compliance with the 1889 Act).

 

The TC units had compressors too.

[jim.snowdon]

13 hours ago, DY444 said:

 

The TC units had compressors too.

I can't disagree, but it seems a pretty pointless exercise, since they would have to be fed off the 750V ETH circuit from the REP or 33. Easier to put an additional compressor on the 4REP if there were any issues of capacity.

 

[DY444]

10 hours ago, jim.snowdon said:

I can't disagree, but it seems a pretty pointless exercise, since they would have to be fed off the 750V ETH circuit from the REP or 33. Easier to put an additional compressor on the 4REP if there were any issues of capacity.

 

 

Standard SR practice was compressors on each unit and the TCs merely continued that. 

 

The ETH thing is a bit of a non-issue too because on a "normal" SR EP emu the compressor is able to run as soon as the master switch in any cab in the formation is moved away from Off.  It's exactly the same on TCs coupled to a REP or 33/1 because the eth supply is automatically switched on as soon as the master switch is moved away from Off in any cab providing the eth interlock circuit is complete.

Edited June 20, 2022 by DY444

[EddieK]

On 03/06/2022 at 19:54, JeremyC said:

Would retention toilets be that difficult a problem to deal with, wouldn't the equipment required be similar to the 'pump out' facilities provided at many boatyards on the canals?

 

A well known heritage railway in North Yorkshire  operates over Network Rail infrastructure to reach Whitby. Any of their vehicles that run to Whitby that have toilets are now fitted with toilet retention tanks on the underframe, and the new carriage shed at Pickering has suitable equipment for tank emptying. The toilet retention tank equipment was funded by Network Rail.